The present invention relates to the manufacture of plastic blow-molded containers having blown finishes, and more particularly, the present invention relates to an injection molded preform, blow-molded intermediate article made from the preform, and method for efficiently displacing, conveying, controlling, and/or rotating intermediate articles within spin trimming machines in a manner which provides improvements in trim consistency and quality.
In the manufacture of blow-molded plastic bottles for containing liquids, such as beverages, it is customary to utilize an injection-molded preform having an injection-molded, narrow-mouth, threaded finish which ultimately forms the threaded finish of the container blown from the preform. The preforms may be injected molded from a variety of desirable plastic materials, such as polyethylene terephythalate (PET). During blow molding, only the body of the preform is expanded, and the injection molded finish is unchanged, remaining in its as-manufactured condition.
Injection molding is a more accurate molding technique in comparison with blow molding. Thus, injection-molded articles are manufactured within tighter tolerances than blow molded articles.
As disclosed in U.S. Pat. No. 6,228,317 assigned to Graham Packaging Company, L.P., assignee of the present application, injection molded preforms have been utilized in the manufacture of hot-fillable PET containers having blown finishes. To this end, the sidewall portion of an injection molded preform is blow molded to form a blown container having a blown finish and a blown moil/accommodation portion projecting from the blown finish. The intermediate article is then conveyed through trimming apparatus to sever the moil portion, which includes an integral injection molded finish, from the blown finish of the container thereby providing a blown container having a blown finish. The severed moil portions and integral injection molded finishes are collected, re-ground, and recycled.
As disclosed in the above referenced ""317 patent, containers made by such a process include hot-fillable and/or retortable wide-mouth jars which have blown threaded finishes and which are utilized to package viscous products, such as, applesauce, spaghetti sauce, relish, pickles, beets, baby foods, sauerkraut, jelly, mayonnaise, and salad dressings to name a few. Other examples of blown finish containers made from injection molded preforms are disclosed in U.S. Pat. No. 4,665,682 issued to Kerins et al.; U.S. Pat. No. 4,618,515 issued to Collette et al.; and U.S. Pat. Nos. 4,576,843 and 4,496,064 issued to Beck et al.
Typically, the blown moil portions of intermediate articles have a pair of longitudinally-spaced outwardly extending projections which define a circumferential inset groove therebetween. See, for instance, the disclosure provided by the above referenced ""317 patent. A drive belt of a trimming machine seats within the groove in the moil portion and conveys, drives and/or rotates the intermediate article within the trimming machine. Thus, as the drive belt advances the intermediate article through the trimming machine, the intermediate article is spin trimmed by a blade or the like which severs the moil portion from the container body. Examples of spin trimmers, moil structures with grooves, and trimmer conveyance mechanisms are disclosed in U.S. Pat. Nos. 4,305,904 and 4,361,531 issued to Black; U.S. Pat. No. 3,675,521 issued to Ziegler; U.S. Pat. Nos. 4,876,930 and 4,445,406 issued to Thatcher; and U.S. Pat. No. 5,257,560 issued to Palazzolo.
Although the above referenced patents disclosing injection molded preforms, blown intermediate articles, and/or methods of manufacturing, conveying and/or trimming containers are satisfactory for their intended purposes, there is a need for improving the handling and control of intermediate articles conveyed within trimming apparatus to improve the trim consistency and trim quality of blown finish containers. To this end, a desirable trimmer drive/conveyance mechanism should positively engage and control an intermediate article at a location possessing greater dimensional stability than the blown moil portion of the intermediate article so that the intermediate article can be conveyed with greater precision and at greater speeds. In addition, it is desirable for the cost of manufacturing blown finish containers to be reduced by decreasing the size of moil portions, thereby reducing the required amount of regrind reprocessing and costs associated therewith. Further, it is desirable to accurately trim the articles to reduce wear and tear of trimming devices, such as blades and the like, thereby increasing the life of the trimming devices and reducing the need for trimmer equipment downtime to replace worn blades. Still further, it is desirable for the accurately conveyed articles to permit the practical use of alternate cutting, trimming, and abrading technologies including ultrasonic, laser and like technologies.
With the foregoing in mind, a primary object of the present invention is to provide a commercially satisfactory blown-finish container having a uniformly and precisely severed peripheral upper edge which ensures proper sealing interaction with a closure.
Another object of the present invention is to provide a high speed precision method of conveying an intermediate article within a spin trimmer to enhance trim consistency and quality while achieving high rates of throughput.
Still another object of the present invention is to provide a preform and intermediate article having an injection molded drive surface which inherently provides improved dimensional stability so that an intermediate article can be conveyed with precision relative to a trimming device to thereby reduce wear and tear of the trimming device and increase the life of the trimming device.
A further object of the present invention is to provide a method of manufacturing a blown finish container which enables commercially acceptable hot fillable and retortable wide-mouth and/or narrow mouth plastic containers to be produced by means of high speed manufacturing equipment in an economical manner that ensures consistent quality and performance.
More specifically, according to one aspect of the present invention, a method is provided for displacing an intermediate article within a trimming machine during the manufacture of a blown-finish, blow molded plastic container. Preferably, the intermediate article has a hollow blow-molded container body with a blown annular finish, a blown accommodation portion projecting from the blown finish, and an injection-molded annular neck portion projecting from the accommodation portion and defining an open top of the intermediate article. The intermediate article is supplied to a trimming machine which has a drive mechanism for displacing, conveying, lifting, and/or rotating the intermediate article within the trimming machine. The drive mechanism of the trimming machine engages the inner peripheral surface, the outer peripheral surface, and/or the end wall of the injection molded neck portion to displace, convey, lift, control and/or rotate the intermediate article within the trimming machine during a moil severing operation. Thus, precise handling and control of the intermediate article is achieved by engaging the injection-molded neck portion of the intermediate article to provide improved trim consistency and quality.
According to another aspect of the present invention, a preform used to manufacture a blow molded plastic article in a blow mold is provided. The preform has a one-piece, injection-molded body with a tubular sidewall portion, a closed bottom end, and a neck portion defining an open end of the preform. The neck portion has an inner peripheral surface, an outer peripheral surface, and an end wall, and at least one of the surfaces provides a drive surface which is readily engagable for purposes of displacing, conveying, lifting, controlling and/or rotating the preform. For example, the drive surface can be either oval or multi-sided or the surface may have at least one recess or the surface may have alternating lugs and recesses. Thus, after the sidewall portion of the preform is blown into a blow molded article in the blow mold, a conveyance/drive mechanism is capable of engaging the drive surface and displacing the blow molded article within a trimming machine.
According to a further aspect of the present invention, an intermediate article formed during manufacture of a blow-molded plastic container is provided. The intermediate article includes an injection-molded neck portion defining an open top of the intermediate article and a hollow blow-molded container body having a sidewall, a closed base, and an annular blown finish. Preferably, the intermediate article also includes a blown accommodation portion which has one end projecting from the annular blown finish of the container body and an opposite end merging into the injection molded neck portion. The neck portion has an inner peripheral surface, an outer peripheral surface, and an end wall. One of the surfaces provides a drive surface which is readily engagable for purposes of displacing the intermediate article within a trimming machine to separate the container body from the accommodation portion and injection-molded neck portion. For example, the drive surface can be either oval or multi-sided or the surface may have at least one recess or the surface may have alternating lugs and recesses.